Generating electric drive and control system



1942- s. H. COWlN 2,292,203

GENERATING ELECTRIC DRIVE AND CONTROL SYSTEM Filed 001;. 11, 1941 llllll 3noentor 52216275 9% (bu/21w a 5! ;y Gttorncgs Patented Aug. 4, 1942 GENERATING ELECTRIC DRIVE AND CONTROL SYSTEM Stuart H. Cowin, Chicago, Ill., assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Application ctobcr11, 1941, Serial No. 414,565

11 Claims.

The present invention relates, generally, to generating electric traction and control systems and more particularly to improvements in such systems and the automatic controls therefor to adapt these systems for use on locomotives of the generating electric type which are subjected to widely variable speeds and loads.

On locomotives of this type, where a number of traction motors are geared to respective driving axles and are supplied with power from a prime mover generator power plant, it is the usual practice to provide manually operated or automatic control means for connecting the motors in series relation with the power plant generator for obtaining high starting torque and for changing from the series to the parallel motor connection for obtaining high speed characteristics from the motors. The conventional control means usually includes means for causing a reduction in the power plant output when the motor connections are changed in order to reduce the current surge and corresponding torque surge resulting from the difference in the electrical constants for these particular motor connections.

It has been found by providing automatic voltage responsive control means which acts at definite values of generator voltage corresponding to definite values of motor and locomotive speed for causing the motor field windings to be shunted when the motors are connected in either a. series or parallel relation with the generator .of the locomotive power plant, and for automatically changing the motor connection relations between the series and parallel relations, that the speed and torque range of the motors may be materially increased for each connection relation, and the current and torque surges may be materially decreased upon a change in these relations, thereby preventing overloading of the power plant and motors and reducing the torque surges thereon and the shocks resulting from these torque surges which are imparted to the locomotive and train pulled thereby. This constitutes the principle object of my invention.

The means by which the above object is accomplished and'other features of my system will be better understood by reference to the following detailed description and the single accompanying drawing illustrating my improved generating electric traction and control system and the electrical connections therefor in diagrammatic form, as arranged for use on generating electric locomotives for which my system is particularly adapted.

Referring now to the drawing, the locomotive power plant includes a prime mover illustrated as a Diesel engine E and an electrical generator of the compound type driven thereby shown generally at G. The engine is provided with any well known type of governor GOV, driven thereby, which acts in response to variations in the speed and load of the power plant to adjust the amount of fuel supplied to the engine to vary the torque, speed and output thereof and also to actuate a generator field rheostat R to vary the generator excitation and therefore the generator output to vary the load on the engine in order to cause.the engine-generator power plant to operate at substantially constant speed and output in awell known manner. The governor is pro,- vided with any well known type of speed setting means, not shown, whereby the power plant may be caused to operate at any one of a number of constant values of speed, torque, load and output. Any well known type of power operated remotely controlled means shown at PO is provided to vary the setting of the governor speed setting means. Any type of power operated means which may be controlled remotely, may be used. Electromagnetic power operated means is shown having the usual train line control conductors connected thereto carried in a train line conduit which is shown extending between the power operated means PO and a master controller MC.

The master controller MC is of a well known type and is provided with a suitable control handle which is movable to a number of control positions for controlling the power operated means PO for causing adjustment of the governor speed setting means and for causing initial energization of a contactor S, which serves to initially connect the traction motors in series relation with the generator when the speed and output of the power plant is increased above a low or idle value, which then causes operation of the automatic control means, to be subsequently described.

The electrical power system includes the compound generator G, a number of traction motors of the series type shown at Ml, M2, M3 and M4, and power conductors and connections shown in heavy lines on the drawing extending therebetween. As shown, the motors MI and M2 are permanently connected in parallel by certain of these power conductors, as are the motors M3 and M4. Also included in these power connections are the series contactor S and parallel contactors PI and P2 which when energized connect each pair of motors in either a series or parallel relation with the generator in a well known manner.

Motor excitation varying means or field shunting means comprising the contactors MI 'BI and MFBIandshuntingresistcrsrl tordarealso provided. Each oi these contactors includes an electromagnet actuating winding and an an armature having a number or contacts fixed thereon and a number of pairs 01' fixed contacts. The upper and lower pair or fixed contacts of each contactor are shown connected in series with a respective shunting resistor across a respective motor series field winding so that upon energisation oi the contactor windings each oi the upper andlowerpairsoi'fixedcontactorswillbe bridged by armature contacts when the armature is attracted and moved upward from the position shown upon energisation or the contactor windings. Br dgingoithesecontactscauseseach motor field winding to be shunted by a respective resistor to reduce the excitation of the motors and therefore cause a reduction in the motor C.I.M.1".,which causesanincreaseinthegenerator current supplied to the motors so that the speed and torque range of the motors is increased materially.

As will be explained later, energization of the windings oi each oi the motor field shunting contactor-s ml and MP8! is accomplished by automatic means which also causes transition oi the motor connection relations with respect to the generator, that is. from the series to the parailel relation. by simultaneously causing de-energintion oi the winding 01' the series contactor 8 and energization of the windings or the parallel contactors PI and P3. This automatic means causes the shunting contactors to operate for either the series or parallel motor connection relations to cause an increase in the speed and torque range of the motors for each motor connection relation. The other pairs of contacts on the field shunting contactors and the series and parallel contactors are interlocking and control contacts and the connections to these contacts and the windings oi these contactors will be described later.

The excitation system oi the enerator includes separately. shunt and series excited excitation circuits. The separately excited circuit includes the previously mentioned field rheostat R, a field winding 8?, a field discharge resistor BPR and a contactor 8P0 which when energized, disconnects the discharge resistor and con- -nects the rheostat and field winding to a battery B to cause normal excitation of the field winding, the excitation current being then limited only by the rheostat R, which, as explained before, is operated by the governor GOV. Upon de-energization of the contactor SPC the field winding SP is simultaneously disconnected from Ste battery and the discharge resistor connected ereacross. The field winding SP supplies the major portion oi the generator excitation, and when it is de-energized the generator voltage is reduced to a negligible value and therefore the power output also is reduced to a negligible value. As will be subsequently described, this action occurs simultaneously with the transfer 01 the motor connections from the series to the parallel connection relation by action of automatic control means, to be described. The discharge resistor SPR, when connected across the winding SP and when this winding is disconnected from the battery, serves to limit the resulting induced voltage therein and prevent damage thereto. The

contactor SPC includes an electromagnetic winding, an armature attracted thereby having contacts fixed thereon and three pairs oi fixed contacts, the lower pair being interlocking and control contacts to be referred to later.

The connections between the rheostat'R, field winding 8P. field discharge resistor SP3 and contactor BPC to accomplish the above described operation will now be described. The upper terminalsoithe rheostatltanddischargeresistor BPRareshownconnectedbyconductors I and. to one contact oi a positive control switch P08. and a positive control conductor PC is also connectedtothisswitchcontactandwillbereterred to later. The other contact or the switch P08 is connecteddirectlytothepositivetcrminaloi'the battery B by a conductor I. and a negative controlconductorNCisshownconnectedtothenclative battery terminal and will also be referred to later. The lower terminal oi the rheostat R isconnectedbyaoonductorltooneterminalol the generatorfield winding 8?, the other terminal oi'whichisconnecudtotheleitupperandcentral fixed contacts oi the contactor SPO by conductors I and ii. The lowerterminaloithewindingand therightupperfixedcontactotthecontaetor SPCareconnectedbyconductors "and lltoa conductor l shown connected between the lower terminaloi'thewindingoiarelayBHCandthe negative control conductor NC. The right fixed central contact orthe contactor BPC'isconnected byaeonductor lltothelowerterminalorthe dischargeresistorSPR. Aconductoritisahown connected between the positive control conductor PC and the master controller MC, and a cornmon negative conductor II for the power operatedmeansPO isconnectedto thenegativecontrol conductor NC, and is shown extending into the train line conduit.

The shunt excitation circuit includes the shunt fieldwindingBRafielddischargeresistorSHR connectedinserieswiththiswindingmndacontactor BBC which, when energised, shunts out the discharge resistor to allow normal values of excitation current to fiow therein. when the contactor BBC is de-energised it causes the discharge resistor to be connected in series with the field winding to materially reduce the current fiow therein and accordingly reduce the generator voltage and output. The windings or both the contactors BPC and BBC are automatically deenergized to cause the voltage and output or the generator to be reduced to a negligible value when transition or the motor connections occurs in response to operation or the automatic control means, to be described. This operation prevents excessive current surges in the power connections, generator, and motor windings. and hence torque surges on the locomotive power plant, traction motors, and means operated thereby. The contactor SHC includes an electromagnetic winding, an armature movable thereby having contacts fixed thereto and two pairs or fixed contacts. The connections between this contactor and the shunt field winding SH and discharge resistor for accomplishing the above described operation are as follows:

The shunt field winding 81-! and field discharge resistor SI-IR. are shown connected in series across the power circuit. One oi the upper fixed contacts or the contactor SHC is connected by a conductor 23 to the same side of the power circuit that one terminal of the discharge resistor is connected to, and the other terminal or the discharge resistor is connected to a conductor 25, which is connceted between the upper left fixed contact of contactor SHC and one terminal of the winding SH. The other terminal of this winding is connected to the .other side of the power circuit. The connections to the lower pair of fixed contacts and upper winding terminal of the contactor will be despeed and torque range of the motors at values of speed and voltage necessary to prevent overloading of the generator and motors and to prevent current and torque surges thereon when these changes occur when the locomotive speed increases I 1. Automatic change in the motor connections from a series relation to a series-shunt connection, that'is, with the motors in series relation with the generator and the motor fields shunted. This change takes place when the voltage rises to a value of 850 volts corresponding to a locomotive speed of 18 M. P. H.

2. Automatic change of the motor connections 1 from the series-shunt to a parallel relation and a simultaneous reduction in the generator output to a negligiblevalue. This change takes place at a voltage of 850 volts corresponding to a locomotive speed of 31 M. P. H.

3. Automatic change of the motor connections from a parallel relation to a parallel-shunt relation, that is, with the motors connected in parallel and the motor fields shunted. This change takes place at a voltage of 850 volts corresponding to a locomotive speed of 50 M. P. 1-1.

When the locomotive speed decreases with the motors connected in parallel-shunt or seriesshunt relation, the following automatic changes in the motor connections take place at 600 volts:

Automatic change of the motor connections from the parallel-shunt connection back to the straight parallel relation occurs when the voltage and speed of the locomotive decrease from a maximum value to a value of 600 volts corresponding to a speed of 45 M. P. H.

Automatic change of the motor connections from the series-shunt to the straight series relation takes place when the voltage and speed decrease to a value of 600 volts corresponding to a speed of 12 M. P. H. The above described automatic operation is controlled by voltage responsive relays shown at VI and V2 and control relays shown at, FBI and PR2. These relays are interconnected and serve to set up and complete holding circuit connections to the previously mentioned contactors to accomplish the above operating sequence and accordingly serve as a counting relay system, as will be described later. The electrical constants of relay VI are such that it closes at 850 volts and opens at 750 volts, and the constants of relay V2 are such that it closes at 700 volts and opens at 600 volts. A forestalling relay shown at FR controlled by a manually operable forestalling switch FS is provided to prevent operation of the relay PR2, which controls energization of the contactors PI and P2 to prevent transition of the motor connections to the parallel connection relatlon when it is desired to obtain low speed and high torque motor characteristics by causing the motors to be retained in a series relation with the generator. Transition of the motor connections from the parallel to the series relation is accomplished manually by opening the forestalling switch FS.

Each of the above relays includes an actuating winding, an armature, having contacts fixed thereon, which is attracted and moved upward to the closed position from the open position in which it is shown, and fixed contacts which are bridged and opened by movement of the armature contacts. The control, interlocking and holding connections "connecting the relays and contactors will now be described in detail.

As previously explained, the master controller is connected to the positive control conductor PC by a conductor l9, and control conductors extending from the controllerto the power operated means P0 are carried in the train line conduit, whereby energization of the power operated means is connected to the positive battery; and a common return conductor 2| carried in the train line conduit is shown connected to the negative control conductor NC. A motor control conductor 21 is also connected between the master controller and the lower left fixed contact of the parallel contactor P2. The two lower left fixed contacts of the relay PR2 are connected by conductors 29 and 30 to the motor control conductor 21. The right lower fixed contact of the relay PR2 is connected by a conductor 3| to the upper winding terminal of the contactor SHC. The left'lower fixed contacts of the contactors P2 and SHC are connected, respectively, by conductors 33 and 34 to the conductor 3|. A conductor 35 is connected between the right lower fixed contact of the contactor PI and the motor control conductor 21 and the left lower fixed contact of contactor PI is connected by a conductor 31 to the upper winding terminal of the series contactor S, the lower winding terminal of which is connected by a conductor 39 to the negative control conductor NC.

The contact arrangement of the master controller, as has been previously explained, allows energization of the series contactor winding to cause closure of this contactor when the controller handle is moved to any control position, which causes the power operated means to cause operation of the power plant at values of speed and output above those obtained at idling speed. When the controller handle is moved to any of these positions the motor control conductor 21 is connected to conductor I9, which is connected to the positive control conductor PC through suitable controller contacts, not shown. The series contactor winding will, accordingly, be energized through the bridged lower contacts of the contactor PI and conductors 21, 35, 31, 39 and negative control conductor NC, and the series contactor S will close to connect the motors Ml to M4 in a series power circuit relation with the generator G. The winding of the contactor SHC will also be simultaneously energized through the bridged lower contacts of the relay PR2 and conductors 21, 29, 30, 3|, l1 and negative control conductor NC. The contactor SHC will close to bridge the lower pair of fixed contacts, one of which is connected by a conductor 34 to the conductor II, and the'other contact is connected by a conductor ll to the upper winding terminal of the relay BPC. The other terminal of relay BPC, as previously mentioned, is connected to the negative control conductor NC by the conductors II and II. The armature of the contactor 8P0 will. accordingly, be attracted and moved upward to the closed position. When the contactors SEC and SP are closed the generator excitation current in both the shunt and separately excited generator fieldwindingsSHandSPwillbeatnormal values. as has been previously explained. and the motorswillbeconnectedinseriesrelationwith the generator.

It will, therefore, be evident that if the controllerhandleismovedtoapositionwherethe poweroperatedmeansPOiscausedtoadjustthe governorspeedsettingmeanssothatthepower plant is caused to operate at constant maximum speed, load and output, constant power input willbesuppliedtothetractionmotorsandthey willexertmaximumstartingtorquetodrivethe locomotive as they are then connected in series Itiswellknownthatforconstantvaluesof power input to series motors and variable loads and speerh thereon the motor voltage vs. motor current curve is an equilateral hyperbola and the voltage is proportional to speed and the motor current is proportional to the motor torque. The torque and current are inversely proportional to speed.

The automatic means by which the motor power connections are changed and by which the motor and generator excitation is controlled actsinresponsetothesevariationsinthegenerator voltage applied to the motors when the motors are connected in difi'erent relations with the generator, and these variations in voltme correspond to variations in the speed of the motors and locomotive. The automatic means, as previously mentioned, comprises the voltage relays VI and V2 and control relays PRI and PR2, serving as a counting relay system.

The windings of the voltage relays VI and V! are connected in parallel across the power circuit by conductors I, ll, 45 and It. The positive control conductor PC is connected to the right lower fixed contact of the relay VI, and the left lower fixed contact is connected by a conductor 41 to a conductor 4!, which is connected between the left fixed contact third from the bottom of the contactor MP8! and a conductor II shown connected between the left fixed contact second from the top of the relay PR! and the left fixed central contact of the contactor PI. The right fixed central contact of the contactor P2 is connected by a conductor 51 to one terminal of a resistor It, and a conductor II is connected between the conductor ll and the right fixed contact second from the top of the relay PR2. The other terminal of the resistor II is connected by a conductor 83 to the upper terminal of the winding of the contactor MFSI, and a conductor I is connected between the conductor II and the upper terminal of the winding of the contactor 1082. The lower terminal of the winding of the contactor MFSI is connected to the right fixed contact of the relay V! by a conductor ll, and a conductor I is connected to the conductor 81 and the negative control conductor NC and also to the lower terminal of the winding of the contactor MFSI. The left fixed contact of the relayviisconnectedtotheconductorllbya conductor".

Itwillbeseenthatthefixedcontactsofthe relay V! are connected across the windings of boththemotor field shunting contacts,andwhen the positive control conupper fixed contact of the by a conductor 0! to the contact of the relay PRI, and lowerfixedcontactofthlsrelayisconby II to a conductor I. which the lower terminal of the PRI and a conductor ll lower terminal of the and the upper left fixed contact of the relay PR2, the upper right fixed contact of which is connected to the positive control conductor PC by a conductor II.

It will be noted that the lower winding terminal of the forestalling relay PR is connected to the negative control conductor NC, and the upper winding terminal is connected by a conductor It to one terminal of a manually operable fores'talling switch PS, the other terminal of which is connected by a conductor III to the motor control conductor 21. These connections permit the forestalllng rela winding to be energiaed only when the forestalllng switch F5 is closed to permit energization of the winding of the relay PR2, which controls energization of the parallel contactors PI and P2 to permit the automatic control means to cause the motor connections to be automatically changed from the series connection relation to the parallel connection relation. as previously described.

Energization of the parallel contactors PI and P2 takes place when the relay PR! is energized and closed through the following conductors: The right fixed contact second from the bottom of relay PR! is connected by a conductor I" to the right lower fixed contact of the contactor SPC. the left lower fixed contact of which is connected by a conductor III to the left central fixed contact of the contactor MFSI. The right central fixed contact of the contactor MFSI is connected by a conductor III to the right lower the contactor MFS2 closes through the bridged fixed contact of the series contactor S, and a conductor I09 is connected between the conductor I01 and the upper winding terminal of contactor Pl, the lower winding terminal of which is connected by a conductor Ill to the negative control conductor NC. The left lower fixed contact of the series contactor S is connected by a conductor H3 to the upper winding terminal of the parallel contactor P2, and the lower winding terminal of the contactor P2 is connected by a conductor H5 to the conductor 39, which is connected to the negative control conductor NC. The central pair of fixed contacts of the parallel contactor Pl are connected by conductors H1 and H9 between the conductors I03 and I01.

Automatic operation for increasing speed of the locomotive Assume that the master controller handle has been moved to a position corresponding to maximum speed, load and output setting of the power plant by the power operated means PO and that the forestalling switch FS is also closed. As previously explained, with the controller in this position the contactors S, SHC and SP are closed to cause a constant maximum value of power to be supplied to the motors, which are then connected in series relation with the generator so that they operate at maximum torque and low speed.

The locomotive will accordingly start, and the speed of the motors and locomotive will increase and the motor C. E. M. F. and generator voltage will increase, causing the generator current to decrease. With the forestalling switch FS closed the forestalling relay winding will be energized through conductors 21, I01, 99 and NC, and this relay will also close.

When the generator voltage increases to a value of 700 volts the voltage relay V2 will close to open the shunt connection across the windings of the motor field shunting contactors MFSI and MFSZ, as described above. Upon a further increase in the speed and voltage the voltage relay V! will close at 850 volts, or at a locomotive speed of 18 M. P. H., which causes energization and closure of the motor field shunting contac tors MFSI and MFSZ. Energization of the windings of these contactors takes place through the following conductors and the bridged contacts: Positive control conductor PC, the bridged lower fixed contacts of relay VI, conductors 41 and 49, the bridged contacts second from the bottom of contactor MFSZ, conductors 53 and 55, the bridged fixed pair of contacts second from the top of relay PR2, conductors BI and 51, resistor 59, and conductors 63, 65, 51, 69 and negative control conductor NC. The resistor 59 is provided to limit the current in this circuit to a safe value. The shunting contactors MFSI and MFS2 will close upon energization of the windings thereof and cause the shunting resistors TI to T4 to be connected in shunt across the respective series field windings of the motors MI to M4 to decrease the C. E. M. F. of the motors, which causes an increase in the current supplied to the motors by the generator and therefore an increase in the motor torque and speed range and a decrease in the generator voltage to a value less than 150 volts, which causes the armature of the voltage relay VI to drop down. Dropping of this armature does not cause de-energization of the windings of the contactors MFSI and MFS2 as a holding circuit is established when pair of fixed contacts third fromthe bottom to these contactor windings through the following conductors: Positive control conductor PC conductors BI, 83, 53 and 55, the bridged fixed contacts second from the top of relay PR2, conductors 6!, 51, resistor 59, conductors 63, 55, 61, 69 to the negative control conductor, and the motors Ml to M4 will accordingly be maintained in the series-shunt connection relation.

Upon closure of the contactors lVLFS2 a circuit will also be established throught the bridged pair of fixed contacts second from the top of this contactor from the positive control conductor PC through conductors 8i and 19, resistor 11, conductors 15 and 13, bridged upper contacts of relay VI, conductor 85, bridged lower contacts of relay PR! and conductors 81, 89 and 90 to the negative control conductor. The resistor 11 is placed in the above circuit to limit the current therein to a safe value. It will be evident that as long as the relay VI is closed and PRI is open, as shown, the winding of the relay FBI is shunted by the bridge upper fixed contacts of relay VI and bridged lower fixed contacts of relay PRI and conductors 13, and 81, but when the relay Vi opens again at 750 volts, the winding of the relay PRI will be energized and close, as. the above described shunt circuit established around the winding of relay PRI will be opened when the upper pair of fixed contacts of this voltage relay are opened after the motor series-shunt power connection relation is completed. Energization and closure of the relay PRI takes place upon closure of the contactor MFSI and opening of the relay VI through conductors NC, BI, 19, resistor 11, conductors 15, 89, and NC. Closure of relay PRI sets up a circuit connection which is completed when the voltage relay VI closes a second time through the bridged lower contacts of the relay VII, the bridged upper contacts of the relay PR! and bridged contacts of the forestalling relay FR to the winding of the relay PR2, which will now be described, to cause transition of the motor connections between the seriesshunt and parallel connection relation with the generator.

When the voltage again increases to a value of 850 volts corresponding to a locomotive speed of 31 M. P. H. with the motors connected in series-shunt power relation with the generator, the voltage relay Vi will close a second time to cause energization of the winding of the relay PR2 through the circuit connection set up, mentioned above, which includes the following conductors: Positive control conductor PC, conductors 41, 49, 93, 9|, 90 and negative control conductor NC. The armature of the relay PR2 will accordingly be attracted and moved upward to the closed position in which the upper pair of fixed contacts and the pair of fixed contacts second from the bottom will be bridged and the lower pair of fixed contacts and the pair of fixed contacts second from the top will be opened simultaneously.

Bridging of the upper pair of fixed contacts of the relay PR2 establishes a holding circuit to the winding of this relay through conductors PC, 91, 95, 93, 9|, 90 and negative control conductor NC as the forestalling relay FR is closed.

Opening of the fixed contacts second from the top of relay PR2 breaks the connection between conductors 55 and 6| through which the windings of the-motor field shunting contactors MFSI and MFSZ are energized, and the armatures thereof with drop to the position shown. Upon the opening oi the two pairs oi fixed contacts second and third from the top oi the contactor MP8! the energizing connection to the winding oi relay PRI comprising conductors Ii and I. and also conductors a and II will be broken, and the armature oitherelayPRl willdrop totheposition shown.

Opening oi the lower pair oi fixed contacts oi the relay PR2 breaks the connection between the conductor SI and conductors 2! and SI through which the winding oi the contactor BHC is'en- 'ergised, causing it to open and thereby opening the connection between conductors 84 and 4| through which the winding oi the contactor SP is energized, and this contactor will also open. With the contactor BI-IC open the discharge resistor BER. will be connected in series relation with the generator shunt field winding to reduce the excitation current therein and the generator output will be reduced, and with the contactor SPO open the generator separately excited field winding 8? will be disconnected irom the battery B and the discharge resistor SPR will be connected across the winding. The generator voltage and power output will, accordingly, be reduced to a negligible value by the opening oi both oi the contactors SEC and BPC,'and the voltage relays VI and V2 will accordingly open.

Bridging oi the fixed contacts second irom the bottom 01' the relay PR2 causes energization oi the winding oi the parallel contactor Pl through these bridged contacts, the bridged contacts oi the contactor SPC and the bridged pair oi central fixed contacts MFSI through the iollowing conductors: 21, it, I, ill, ill, III, III and negative control conductor NC to cause the armature oi the contactor Pi to be attracted and moved upward. Initial upward movement oi this armature causes the central pair oi fixed contactstobebridgedandalsotoretainthelower pair oi fixed contacts bridged until the upper pair oi fixed contacts are bridged. The two lower pairs oi contacts are flexible and iormed as shown to accomplish this action: Bridging oi the central pair oi contacts establishes a holding circuit, comprising conductors 21, III, ill, I" and Ill, to the winding oi contactor Pi, and when the upper pair of power contacts oi this contactor are bridged by iurther movement oi the armature the lower pair of contacts will then be opened to break the energizing circuit to the winding oi the series contactor 5 comprising conductors II and I1. and its armature will accordingly drop to the position shown. With the armature oi contactor B in the position shown the lower pair oi interlocking contacts will be bridged to cause energimtion oi the winding oi contactor P2 through conductors I", Hi, III, III, Iii and ll to cause upward movement oi its armature and bridging oi the upper pair oi power contacts and both pairs oi interlocking contacts to establish the parallel power circuit relation oi the motors with respect to the generator. It will be evident that by preventing the series contactor 8 irom opening beiore the parallel contactor P2 closes, by providing flexible contacts on the armature oi the contactor Pl the power circuit is not opened during transition oi the motor connections. thereby preventing arcing and burning oi the contacts of these contactors.

Upon the completion oi the parallel motor power connection by opening oi the series contactors and closing oi the parallel contactor P2, the generator separately excited field winding 76 S? will be reconnected to the battery B and the discharge resistor SHR will be shunted out oi the generator shunt ileld circuit to cause the power oumut oi the generator to the motors to be again increased to the original value in the iollowing manner.

Bridging oi the lower pair oi fixed contacts oi the parallel contactor P2 causes the winding oi the contactor BBC to be energized through the iollowing conductors: motor control conductor 21, conductors II, it and II to the negative control conductorNC, to cause closure oi this contactor which then causes the contactor SP6 to be energized and close in the manner described previously.

Bridging oi the central pair oi fixed contacts oi the contactor PI causes the conductors ll and H to be connected thereby setting up a circuit to be described subsequently, which is completed upon the next or third successive closure oi the relay Vi duetoanincreaseinthespeedoithe locomotive to again cause energization and closure of the motor field shunting contactors mi and MP8! to iurther increase the torque and speed range oi the motors and thereby cause the motors and locomotive to operate at maximum speed.

Aiter transition oi the motor connections the current output oi the generator to the motors is again increased and their torque and speed will increase. When the voltage applied to the motors and relay V2 again increases to a value oi 700 volts the relay V! will close a second time and again open the shunt circuit across the windings oi the motor fieldshunting contactors mi and MP8! in the same manner as described previously. Upon a iurther increase in the motor and locomotive speed to a value oi 50 M. P. H. the value oi voltage. applied to the motors and winding oi relay Vi will be 850 volts. and the relay Vi will close the third time to again cause energization and closure oi the contactors MFSI and MP8! through the bridged lower contacts oi the relay Vi, the bridged contacts second irom the bottom oi contactor MFBI, the bridged central pair oi fixed contacts oi the contactor P2, and conductors PC, I, ll, ll, II, 55 and 81, resistor II and conductors 63, ll, 01, N and negative control conductor NC, to cause the motors to be connected in the parallel-shunt power relation with the generator and to operate and drive the locomotive at maximum speed.

Automatic operation [or decreasing speed 0/ the locomotive Upon a decrease in the locomotive irom the maximum speed value to a speed oi 45 M. P. H. due to an increase in the load thereon the voltage applied to the motors and winding oi relay V! will decrease to a value oi 600 volts and cause the relay V2 to be de-energized and open to complete the shunt circuit across the windings oi the motor field shunt contactors M78! and MP8! and cause de-energization thereoi, causing these contactors to open and change the motor connection from the parallel-shunt power relation back to the straight parallel power connection relation with the generator. The shunt connection established across the windings oi the contactors MFSI and mi comprises the conductors l1 and Ii and II which are connected by bridging oi the fixed contacts oi the relay V! by the armature contact.

Transition backward irom the parallel motor connection relation to the series-shunt relation may be accomplished manually by opening of the forestalling switch FS. When the forestalling switch FS is opened the forestalling relay is de-energized and opens, to open the single energizing connection to the winding of the relay PR2, comprising the conductors 93 and 9|, and the relay PR2 accordingly opens to break the previously described energizing connection to the parallel contactors PI and P2. The connection arrangement shown makes it necessary that the forestalling switch FS be closed to cause energization and closure of the forestalling relay FR to permit energization and closure of the relay PR2 in order to cause energization and closure of the parallel contactors PI and P2 to complete the parallel motor connection relation. When the parallel contactor Pl opens, the series contactor is energized through the bridged lower fixed contacts of the contactor PI, and the series contactor accordingly closes to connect the motors in series relation with the generator and causes de-energization of the contactor P2 by opening of the lower fixed contacts of the series contactor S.

The motor field shunting contactors MFSI and MFSZ will close if the locomotive speed is above 18 M. P. H., which causes energization of the relays VI and V2, as described previously.

Automatic change in the motor connection relation between the motor series-shunt and series power relations takes place at 12 M. P. H. upon de-energization of the relay V2, as previously described.

In order to disconnect the motors from the generator and to decrease the output of the power plant the master controller handle is moved to a position to disconnect the motor control conductor 21 from the conductor l9 connected to the positive control conductor PC to cause de-energization of contactors S, SEC and SPC, which causes their armatures to move to the position shown, which, as previously described, opens the motor series power connection relation with respect to the generator and causes the output of the generator to be reduced to a negligible value. As also previously described, with the controller in this position the power operated means PO adjusts the governor speed setting means to cause operation of the engine at idling speed.

It will be evident that transition from the parallel-shunt motor connection to the seriesshunt connection can be made by opening the forestalling switch and that the motors may be disconnected from the generator at any speed of the locomotive by moving the handle of the master controller back to the position at which the power plant is caused to run at idling speed and negligible output.

The electrical constants of the series, seriesshunt, parallel and parallel-shunt power circuits are such that if the connections are changed at the values of speed and corresponding values of voltage specified, overloading of the engine-generator power plant and motors will be prevented, as the available power output of the power plant is maintained equal to the power demand of the motors by the governor, and current surges and resulting torque surges are held to a minimum value, as they cause changes in the motor circuit relations at proper values of voltage and speed for the particular circuit relations changed. It

will be evident that for other circuit relations the automatic control means may be adjusted to cause operation similar to that described above.

I claim:

1. A locomotive generating electric drive and control system comprising a prime mover generator power plant, traction motors supplied with power from the power plant, speed, load and output regulating means for the power plant, excitation reducing means for the motors, a power circuit including switching means for connecting the motors in difierent circuit relations with the power plant generator, automatic control means for said motor excitation reducing means and said switching means, said automatic control means acting in response to different preselected values of voltage of the generator corresponding to variations in the speed and load on the motors for each motor circuit relation with and without the excitation of the motors reduced, automatically to reduce and increase the motor excitation for each motor circuit relation and to cause a change from one motor circuit relation to the other automatically, and manually operable control means for controlling the power plant speed, load and output regulating means and for controlling said switching means in order to establish one motor circuit relation and thereby permit operation of said automatic control means.

2. A locomotive generating electric drive and control system comprising a prime mover generator power plant, speed, load and output regulating means therefor, traction motors supplied with power from said power plant generator, motor excitation reducing means, power connections including switching means for connecting the motors in difierent circuit relations with the generator, manually operable control means for said power plant regulating means and said switching means to establish one motor circuit relation with the generator when the power plant is caused to operate at high speed, load and output, automatic control means acting in response to preselected values of generator voltage corresponding to different values of motor speed and load for each of said motor circuit relations with or without the motor excitation reducing means operative, said automatic means being connected to said motor excitation reducing means and said switching means by interlocking and control connections so that the motor excitation may be automatically increased or decreased for each motor circuit relation and so that the circuit relation established by the manually operable means is automatically changed to another circuit relation by said automatic control means to increase the speed and torque range of the motors without overloading the power plant, and manually controlled forestalling means to prevent control of said motor excitation reducing means and said switching means by said automatic control means.

3. A locomotive generating electric drive and control system comprising a prime mover generator power plant, power plant speed, load and output regulating means, excitation reducing means for the power plant generator, series traction motors for driving the locomotive, shunting means for the motor field windings, power connections including switching means for connecting the motors in series or parallel relation with the generator, automatic control means acting in sequence and in response to preselected values of generator voltage corresponding to difierent values of motor and vehicle speed with the motors connected in either series or parallel relation either with or without the motor fields shunted to control the motor field shunting means and also to control the switching means and generator excitation reducing means simultaneously to cause transition from the series motor connection with the motor fields shunted to the parallel motor connection relation, and a manually operable controller for controlling said switching means and power plant speed, load and output regulating means to Jointly establish the series motor connection relation and to vary the power supplied to the motors to cause variation in the speed and torque thereof and operation oi the automatic control means in the manner described.

4. A generating electric drive and control system for a vehicle comprising a prime mover generator power plant, output regulating means therefor, excitation reducing means for the power plant generator, a plurality oi vehicle traction motors, field shunting means for the motors to increase the inherent speed and torque range thereof, a power circuit between the generator and motors which include means for connecting the motors in a series or parallel relation with the generator, automatic control means for the motor field shunting and connecting means adapted to act at preselected values oi generator voltage corresponding to difierent values of speed of the motors for each of said motor connection relations to control said motor field shunting means to increase the speed and torque range of the motors and to act when the motors are connected in series relation with their fields shunted to control both said generator excitation reducing means and said motor connecting means to simultaneously cause a reduction in the generator output to the motors and transition oi the motor connections to the parallel connection relation, and manually operable control means Jointly controlling the motor connecting means and I power plant output regulating means to establish the series connection relation when the power plant is caused to operate at minimum output.

5. A generating electric drive and control system for a vehicle comprising a prime mover generating power plant, speed and torque varying means for the prime mover, excitation varying means for the generator to vary the load on the prime mover, prime mover speed responsive means for actuating both the prime mover speed and torque varying means and generator excitation varying means to cause operation of the power plant at constant output, means for varying the speed response or the speed responsive means to vary the speed, load and output oi the power plant, vehicle traction motors for driving the vehicle, a power circuit including switching means for the connection of the motors in series or parallel relation with the generator and field shunting means for the motors, and control means comprising a manually operable master controller for jointly controlling the switching means and the means varying the speed response of the speed responsive means to cause the motors to be initially connected in series relation withthe generator and thereafter to cause operation oi the power plant and increasing values 01' power output to the motors and automatic control means responsive to preselected values of generator voltage corresponding to difierent increasing values oi the motor and vehicle speed to automatically control the generator excitation varying means and switching means in a proper sequence to initially cause the motor fields to be shunted when the motors are connected in series relation, to next cause transition between the series and parallel motor connection relations and a drastic reduction in the enerator excitation and power supplied to the motors by the generator during transition of the connections and to finally cause the motor fields to be shunted when in the parallel connection relation, the above sequence oi operation causing the motors and vehicle to be accelerated from rest to maximum speed with minimum shock to the vehicle and driving means therefor.

6. A locomotive generating electric drive and control system comprising a plurality of series traction motors, field shunting means therefor to vary the normal speed and torque range thereoi, a prime mover generator power plant for the motors, speed, load and output varying means for the power plant, generator excitation reducing means to substantially reduce the power supplied to the motors, motor connecting means for relating the motors in a series or parallel relation with the generator, manual control means for the power plant output regulating means and motor connecting means to initially cause the motors to be connected in series relation and the output of the power plant to be thereafter increased, an automatic counting relay system acting in response to preselected values of generator voltage resulting from an increase in the speed of the motors and vehicle to control the motor field shunting means, generator excitation varying means and motor connecting means to successively cause the motor fields to be shunted when the motors are connected in series relation, to cause next a simultaneous reduction in the generator excitation and transition of the motors to the parallel connection relation and finally to cause the motor fields to be shunted when the motors are connected in parallel relation.

7. A locomotive generating electric drive and control system comprising a pluralityoi series traction motors, field shunting means for the motors, a prime mover generator power plant, speed, load and output regulating means for the power plant, generator excitation interrupting means, a power circuit between the generator and motors including contactors for connecting the motors in a series-parallel or parallel relation with the generator, manual control means to: initially controlling the contactors for establishing the series-parallel motor connection and for controlling the output regulating means 01 the power plant, and automatic control means acting in response to variations in the generator voltage resulting from variations in the speed or the motors for jointly controlling the generator excitation interrupting means and contactors in order to cause transition from the series-parallel to the parallel connection to increase the speed and torque range of the motors without imparting shocks to the motors. said automatic means also acting at corresponding values of voltages but at difierent values of motor and vehicle speeds for each of the motor connection relations to control the motor field shunting means in order also to increase the speed and torque range of the motors for each motor connection relation and to reduce the current surges and therefore the shocks imparted to the locomotive when transition oi the motor connections is accomplished by the automatic control means.

8. A locomotive generating electric drive and control system comprising a prime mover generator power plant, speed, load and output regulating means therefor, said power plant generator having sell and separately excited fields and excitation reducing means associated therewith tor reducing the excitation current in said fields to a negligible value, a plurality of pairs of traction motors permanently connected in series relation, excitation varying means for said motors, a power circuit between themotors and generators including switching means for connecting pairs of motors in series or parallel relation, an automatic counting relay system comprising a plurality oi relays acting in succession at difierent preselected values of generator voltage corresponding to variation in the speed of the motors when the motors are connected in series or parallel relation with or without the motor fields shunted, a plurality of control relays interconnected with said voltage 'relays and also with said generator excitation reducing means, said motor excitation varying means and said switching meansin such manner-that control and holding circuits are successively set up and completed to 7 cause operation of the motor excitation varying means prior to and after simultaneous operation of the switching means and generator excitation reducing .means by action of said automatic counting relay mechanism to cause transition between the series' and parallel motor connection, the above sequence of operation by said automatic counting relay system causing successive variations in the speed and torque range of the motors without overloading the generator or without causing shocks on the motors or generator,-and manually operable control means for I jointly control1ing the power plant-output regulating means and the switching means to vary the generator power output to the motors and to establish the series motor connection relation. *92 A locomotive drive and control system comprising a power plant including a generator, a

plurality of traction motors, excitation reducing means for the motors, circuit connections between the generator and motors including switching.

means acting in response to the changes in the generator and motor voltage for automatically controlling the switching means to cause a change in motor circuit relations and to cause the motor excitation to be reduced in proper sequence.

10. A locomotive drive and control system comprising a power plant including a generator, output regulating means for the power plant, a plurality of traction motors, excitation varying means for the motors, circuit connections between the generators and motors including switching means to change the motor circuit relations with respect to the generator and to render the motor excitation varying means operative, manual means for controlling the switching means to establish one motor circuit relation with the generator and to control the power plant output regulating means, and means responsive to generator voltage to control the switching means and power plant output regulating means simultaneously and for separately controlling the motor excitation means to prevent overloading and shocks on the power plant and motors.

11. A locomotive drive and control system comprising a power plant including a generator, generator output regulating means, a plurality of traction motors, motor excitation regulating means, circuit connections between the generator and motors including switching means to change the motor circuit relations and to render the 

